[meteorite-list] article of interest in "Nature"

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Fri, 27 Apr 2007 02:00:49 -0500
Message-ID: <093e01c78899$cab805a0$862e4842_at_ATARIENGINE>

Hi, Jerry, List,

    Here's the abstract:

    "The abundance of chlorine in the Earth
is highly depleted relative to carbonaceous
chondrites and solar abundances. Knowledge
of the Cl concentrations and distribution on
Earth is essential for understanding the origin
of these depletions. Large differences in the
stable chlorine isotope ratios of meteoritic,
mantle and crustal materials have been used
as evidence for distinct reservoirs in the solar
nebula and to calculate the relative proportions
of Cl in the mantle and crust. Here we show,
using a new analytical procedure, that these
large isotopic differences do not exist, and
that carbonaceous chondrites, mantle and
crust all have the same 37Cl/35Cl ratios.
There is no evidence for multiple nebular
reservoirs with distinct isotopic compositions.
That is to say, there is no evidence to support
addition to the crustal/atmospheric reservoir
of late material of cometary origin. We have
further analyzed crustal sediments from early
Archean to Recent and find no isotopic
variations with age, demonstrating that the
mantle and crust have always had the same
d37Cl value. The similarity of mantle, crust
and carbonaceous chondrites establishes
that there was no isotopic fractionation
during differentiation of the Earth and no
late Cl-bearing volatile additions to the crustal
veneer with unique isotopic composition."

    Translation:

    "Despite the fact that there are big differences
in the amount of chlorine in the Earth's crust and
mantle (on the one hand) and carbonacious chondrites
and the Sun (on the other hand), we think the ratio
of stable isotopes everywhere in the solar system
is the same (even though other folks get different
measurements), and that proves that everything
came out of the same cookpot, 'cause our method
of measuring is better than theirs."

    Specifically, they want to shoot down the idea
that there was a last-minute accretion of comets and
such on the surface of the Earth that would explain
why crust is so different than mantle. Presumably,
this would also shoot down the idea that the Earth's
water was brought to it largely by comets.

    The quarrel we call "knowledge" goes on...


Sterling
-------------------------------------------------------------
----- Original Message -----
From: "Gerald Flaherty" <grf2 at verizon.net>
To: <Meteorite-list at meteoritecentral.com>
Sent: Thursday, April 26, 2007 9:33 PM
Subject: [meteorite-list] article of interest in "Nature"


"Chlorine isotope homogeneity of the mantle, crust and carbonaceous
chondrites
            Z. D. Sharp et al.
            Nature
            doi: 10.1038/nature05748
            First Paragraph | Full Text | PDF"
I only get these text messages with no links but if anyone who has access to
Nature cares to explore and "report" ?
Jerry Flaherty

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Received on Fri 27 Apr 2007 03:00:49 AM PDT